AD 94-25-06

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Model DC-9-80 series airplanes and Model MD-88 airplanes series airplanes was published in the Federal Register on July 27, 1994 (59 FR 38147). That action proposed to require modification of the left and right engine nose cowls.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

One commenter supports the propose rule.

Several commenters request that the compliance time for the accomplishment of the modification be extended from the proposed 8 months to 12 or 18 months. These commenters state that they would have to special schedule their fleet of airplanes to accomplish this modification within the proposed compliance time. This would entail considerable additional expenses and schedule disruptions. The FAA concurs. The FAA's intent was that the modification be accomplished during a regularly scheduled maintenance for the majority of the affected fleet, when the airplanes would be located at a base where special equipment and trained personnel would be readily available, if necessary. Based on the information supplied by the commenters, the FAA now recognizes that 12 months corresponds more closely to the interval representative of most of the affected operators' normal maintenance schedules. Paragraph (a) of the final rule has been revised to reflect a compliance time of 12 months. The FAA does not consider that this extension of an additional 4 months for compliance will adversely affect safety.

Two commenters state that, during accomplishment of the modification, they found an interference condition on the engine cowls being modified that prevents installation of bolt heads facing forward. One commenter states that the final rule of this AD should not be released until the McDonnell Douglas MD-80 Alert Service Bulletin A71-61 is revised to correct procedures relative to this interference condition. The FAA infers from these commenters that they would like the proposed rule to be revised to cite the latest revision of McDonnell Douglas MD-80 Alert Service A71-61. The FAA concurs. Since issuance of the proposed rule, the FAA has reviewed and approved Revision 1, of McDonnell Douglas Alert Service Bulletin, dated October 4, 1994. Revision 1 allows the installation of bolts from the engine flange side when interference with the Hi-Lok bolts exist. The FAA has revised paragraph (a) of the final rule to reflect the latest revision to the alert service bulletin as an additional source of service information.

The FAA has recently reviewed the figures it has used over the past several years in calculating the economic impact of AD activity. In order to account for various inflationary costs in the airline industry, the FAA has determined that it is necessary to increase the labor rate used in these calculations from $55 per work hour to $60 per work hour. The economic impact information, below, has been revised to reflect this increase in the specified hourly labor rate.

As a result of recent communications with the Air Transport Association (ATA) of America, the FAA has learned that some operators may misunderstand the legal effect of AD's on airplanes that are identified in the applicability provision of the AD, but that have been altered or repaired in the area addressed by the AD. Under these circumstances, at least one operator appears to have incorrectly assumed that its airplane was not subject to the AD. On the contrary, all airplanes identified in the applicability provision of an AD are legally subject to the AD. If an airplane has been altered or repaired in the affected area in such a way as to affect compliance with the AD, the owner or operator is required to obtain FAA approval foran alternative method of compliance with the AD, in accordance with the paragraph of each AD that provides for such approvals. A note has been added to the final rule to clarify this requirement.

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

There are approximately 1,062 McDonnell Douglas McDonnell Douglas Model DC-9-80 series airplanes and Model MD-88 airplanes of the affected design in the worldwide fleet. The FAA estimates that 540 airplanes of U.S. registry will be affected by this AD, that it will take approximately 6 work hours per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts will cost approximately $100 per airplane. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $248,400, or $460 per airplane.

The FAA has been advised that 74 U.S.-registered airplanes have been modified in accordance with the requirement of this AD. Therefore, the future economic cost impact of this rule on U.S. operators is now only $214,360.

The regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOTRegulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39 - AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

§ 39.13 - (Amended)

2. Section 39.13 is amended by adding the following new airworthiness directive: